1. Field of the Invention
The present invention generally relates to an electro-optical arrangement for and method of collecting and displaying information in real time along a line of sight from a human operator to remote targets located at variable distances therefrom and identifiable by machine-readable indicia and, more particularly, to automatically displaying a two-dimensional image on each target adjacent its indicia along the line of sight while maintaining a size of the image relatively constant over an extended range of the distances.
2. Description of the Related Art
It is generally known to project a two-dimensional image on a screen based on a pair of scan mirrors which oscillate in mutually orthogonal directions to scan a laser beam over a raster pattern. However, the known image projection systems have limited resolution, typically less than a fourth of video-graphics-array (VGA) quality of 640×480 pixels. Also, the image produced by the known projection systems is typically only sharp and clear at a single distance, or at most, a limited range of distances, away from the systems. The physical size and power consumption of the known projection systems are relatively high, thereby rendering them impractical for use in miniature, battery-operated, operator-wearable, hand-held or finger-supported applications.
It is also generally known to display an image on a screen of a data collection terminal worn on an operator's wrist or belt. Data is entered in such wrist- or belt- worn terminals, either manually by keyboard entry, or automatically by an electro-optical reader mounted on the back of one or more of the operator's fingers. The data captured by the reader is sent by wired or wireless link to the terminal, and information corresponding to the captured data is displayed on the terminal screen, typical a liquid crystal display (LCD) device. See, for example, U.S. Pat. No. 5,578,810; No. 5,410,140; No. 5,543,610 and No. D-391,250, for examples of known finger-mounted optical readers.
Experience has shown, however, that the known data collection systems that employ a wrist- or belt- worn terminal coupled to a finger-mounted reader are not altogether satisfactory due to the requirement that the operator has to repeatedly redirect his/her line of sight during use. Under normal operation, the operator initially directs his/her eyes along a line of sight to indicia, such as a bar code symbol, typically printed on a label affixed to a target, such as a parcel to be delivered. The operator aims the reader at the symbol, initiates a scan, and then waits for auditory or visual confirmation that the symbol has been successfully read.
The system then processes the data collected by the reader and typically displays information related to the processed data on the terminal. Since the terminal is mounted, as previously described, on one's wrist or belt, the operator must turn his/her head, or at least redirect the focus of his/her eyes along a different light of sight in order to see the displayed information on their wrist or belt. When performing multiple repeated scans of successive symbols on successive targets, this constant redirection of one's eyes slows productivity and causes discomfort.